Reconstruction of early Cambrian ocean chemistry from Mo isotopes

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	Reconstruction of early Cambrian ocean chemistry from Mo isotopes
	Hanjie Wen; Haifeng Fan; Yuxu Zhang; Christophe Cloquet; Jean Carignan
刊名	Geochimica et Cosmochimica Acta
	2015
卷号	164 期号:1 页码:1-16
英文摘要	The Neoproterozoic-Cambrian transition was a key time interval in the history of the Earth, especially for variations in oceanic and atmospheric chemical composition. However, two conflicting views exist concerning the nature of ocean chemistry across the Precambrian-Cambrian boundary. Abundant geochemical evidence suggests that oceanic basins were fully oxygenated by the late Ediacaran, while other studies provide seemingly conflicting evidence for anoxic deep waters, with ferruginous conditions [Fe(II)-enriched] persisting into the Cambrian. Here, two early Cambrian sedimentary platform and shelf-slope sections in South China were investigated to trace early Cambrian ocean chemistry from Mo isotopes. The results reveal that early Cambrian sediments deposited under oxic to anoxic/euxinic conditions have delta Mo-98/95 values ranging from -0.28 parts per thousand to 2.29 parts per thousand, which suggests that early Cambrian seawater may have had delta Mo-98/95 values of at least 2.29 parts per thousand, similar to modern oceans. The heaviest and relatively homogeneous delta Mo-98/95 values were recorded in siltstone samples formed under completely oxic conditions, which is considered that Mn oxide-free shuttling was responsible for such heavy delta Mo-98/95 value. Further, combined with Fe species data and the accumulation extent of Mo and U, the variation of delta Mo-98/95 values in the two studied sections demonstrate a redox-stratified ocean with completely oxic shallow water and predominantly anoxic (even euxinic) deeper water having developed early on, which eventually became completely oxygenated. This suggests that oceanic circulation at the time became reorganized, and such changes in oceanic chemistry may have been responsible for triggering the "Cambrian Explosion" of biological diversity.
学科主题	矿床地球化学
语种	英语
公开日期	2017-05-17
内容类型	期刊论文
源URL	[http://ir.gyig.ac.cn:8080/handle/352002/6044]
专题	地球化学研究所_矿床地球化学国家重点实验室_矿床地球化学国家重点实验室_期刊论文
推荐引用方式 GB/T 7714	Hanjie Wen,Haifeng Fan,Yuxu Zhang,et al. Reconstruction of early Cambrian ocean chemistry from Mo isotopes[J]. Geochimica et Cosmochimica Acta,2015,164(1):1-16.
APA	Hanjie Wen,Haifeng Fan,Yuxu Zhang,Christophe Cloquet,&Jean Carignan.(2015).Reconstruction of early Cambrian ocean chemistry from Mo isotopes.Geochimica et Cosmochimica Acta,164(1),1-16.
MLA	Hanjie Wen,et al."Reconstruction of early Cambrian ocean chemistry from Mo isotopes".Geochimica et Cosmochimica Acta 164.1(2015):1-16.